If Roberto scored 85, what was his z-score?

Question

On a nationwide math test, the mean was 75 and the standard deviation was 10. If Roberto scored 85, what was his z-score?

Answer 1

z = (x-mu)/sigma

x = value

mu = known population mean

sigma = known population standard deviation

z = (85-75)/10 =1.0

he is in the top 16% of the population taking the test,

the 84th percentile, according to the normal distribution.